1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine, for example, and in particular, relates to a stator construction for an automotive alternator mounted to an automotive vehicle such as a passenger car or a truck.
2. Description of the Related Art
FIG. 22 is a cross section showing a conventional automotive alternator, and FIG. 23 is a perspective showing a stator of the conventional automotive alternator.
In FIGS. 22 and 23, the automotive alternator is constructed by rotatably mounting a Lundell-type rotor 7 by means of a shaft 6 inside a case 3 constructed from an aluminum front bracket 1 and an aluminum rear bracket 2, and fastening a stator 50 to an inner wall of the case 3 so as to cover an outer circumferential side of the rotor 7.
The shaft 6 is rotatably supported in the front bracket 1 and the rear bracket 2. A pulley 4 is fastened to a first end of this shaft 6 so that rotational torque from an engine can be transmitted to the shaft 6 by means of a belt (not shown).
Slip rings 9 for supplying electric current to the rotor 7 are fastened to a second end of the shaft 6, and a pair of brushes 10 are housed in a brush holder 11 disposed inside the case 3 such that the pair of brushes 10 slide in contact with the slip rings 9. A regulator 18 for adjusting the magnitude of alternating voltage generated in the stator 50 is fastened by adhesive to a heat sink 17 fitted onto the brush holder 11. A rectifier 12 which is electrically connected to the stator 50 and converts alternating current generated in the stator 50 into direct current is mounted inside the case 3.
The rotor 7 is composed of a rotor coil 13 for generating magnetic flux on passage of electric current, and a pair of pole cores 20 and 21 disposed so as to cover the rotor coil 13, magnetic poles being formed in the pole cores 20 and 21 by magnetic flux generated in the rotor coil 13. The pair of pole cores 20 and 21 are made of iron, each has six claw-shaped magnetic poles 22 and 23 disposed on an outer circumferential perimeter at even pitch in a circumferential direction so as to project axially, and the pole cores 20 and 21 are fastened to the shaft 6 facing each other such that the claw-shaped magnetic poles 22 and 23 intermesh. In addition, fans 5 are fastened to first and second axial ends of the rotor 7.
The stator 50 includes: a cylindrical stator core 51 formed with a number of slots 51a extending axially at a predetermined pitch in a circumferential direction; a stator winding 52 wound onto the stator core 51; electrically-insulative resin portions 25 composed of epoxy resin or the like molded around front-end and rear-end coil ends 52a and 52b of the stator winding 52; and insulators (not shown) installed in each of the slots 51a for electrically insulating the stator winding 52 from the stator core 51. In this case 3, the stator core 51 is formed with thirty-six slots 51a at even pitch so as to house one three-phase alternating current winding such that the number of slots housing each winding phase group corresponds to the number of magnetic poles (twelve) in the rotor 7.
Air intake openings 1a and 2a are disposed in axial end surfaces of the front bracket 1 and the rear bracket 2, and air discharge openings 1b and 2b are disposed in two outer circumferential shoulder portions of the front bracket 1 and the rear bracket 2, facing the radial outside of the front-end and rear-end coil ends 52a and 52b of the stator winding 52.
Next, the method of constructing the conventional stator 50 will be described with reference to FIGS. 24 to 27.
First, belt-shaped bodies having protrusions and recesses are prepared from belt-shaped thin sheets composed of SPCC material being a magnetic material. Then, a parallelepiped laminated core 55, shown in FIG. 24, is prepared by laminating a predetermined number of sheets of the belt-shaped bodies and laser welding an outer portion thereof. Thirtysix slots 55a are formed on one side of this laminated core 55.
A stator winding group 57A having an overall flat shape is prepared by winding one strand of wire 56 a predetermined number of turns in a wave winding at a pitch of three slots, the strand of wire being composed of an insulated copper wire material having a circular cross section. The winding start and finish ends of the strand of wire 56 constituting this stator winding group 57A become an output wire 56a and a neutral-point 56b, respectively. In addition, stator winding groups 57B and 57C are similarly prepared by winding a single strand of wire 56 in each case.
Thereafter, the three stator winding groups 57A, 57B, and 57C are superposed so as to be offset by a pitch of one slot and installed in the laminated core 55 by inserting each respective winding group into every third slot 55a as shown in FIG. 25. Thus, the three stator winding groups 57A, 57B, and 57C are installed in the laminated core 55 as shown in FIG. 26.
Next, the laminated core 55 is bent into a cylindrical shape by means of a shaping device (not shown). Then, the ends of the laminated core 55 are abutted and laser welded to each other to obtain a cylindrical stator core 51. Thus, a stator is obtained with the three stator winding groups 57A, 57B, and 57C wound into the stator core 51 as shown in FIG. 27.
In addition, the coil ends of the stator winding groups 57A, 57B, and 57C are molded into the electrically-insulative resin portions 25 to obtain the stator 50 shown in FIG. 23.
In the stator 50 constructed in this manner, the neutral-points 56b of each strand of wire 56 constituting the stator winding groups 57A, 57B, and 57C are connected to obtain the stator winding 52 which is a three-phase alternating-current winding. These stator winding groups 57A, 57B, and 57C have a mutual phase difference of 120xc2x0 and correspond to an a-phase, b-phase, and c-phase winding group, respectively, of the three-phase alternating-current winding. The output wires 56a of each strand of wire 56 constituting the stator winding groups 57A, 57B, and 57C are connected to the rectifier 12.
In the automotive alternator constructed in this manner, electric current is supplied from a battery (not shown) through the brushes 10 and the slip rings 9 to the rotor coil 13, generating magnetic flux. The claw-shaped magnetic poles 22 of the first pole core 20 are magnetized with north-seeking (N) poles by this magnetic flux, and the claw-shaped magnetic poles 23 of the first pole core 21 are magnetized with south-seeking (S) poles. At the same time, rotational torque from the engine is transmitted through the belt and the pulley 4 to the shaft 6, rotating the rotor 7. Thus, a rotating magnetic field is applied to the stator winding 52, generating electromotive force in the stator winding 52. This alternating electromotive force passes through the rectifier 12 and is converted into direct current, the magnitude of the voltage is adjusted by the regulator 18, and the battery is recharged.
At the rear end, external air is drawn in through the air intake openings 2a disposed opposite the heat sink of the rectifier 12 and the heat sink 17 of the regulator 18, respectively, by rotation of the fans 5, flowing along the axis of the shaft 6, cooling the rectifier 12 and the regulator 18, and is then deflected centrifugally by the fans 5, cooling the rear-end coil end 52b of the stator winding 52 before being expelled to the outside through the air discharge openings 2b. At the same time, at the front end, external air is drawn in axially through the air intake openings 1a by rotation of the fans 5, and is then deflected centrifugally by the fans 5, cooling the front-end coil end 52a of the stator winding 52 before being expelled to the outside through the air discharge openings 1b. 
In the conventional stator 50, each of the stator winding groups 57A, 57B, and 57C constituting the stator winding 52 is prepared by wave winding one strand of wire 56 for a predetermined number of turns at a pitch of three slots, the winding groups being wound into every third slot 51a with each winding group offset from the next by one slot so as to constitute an outer layer, an intermediate layer, and an inner layer in the radial direction.
Thus, because the turn portions of the strands of wire 56 constituting the coil ends are not aligned so as to be stacked in the circumferential direction, it is difficult to mold the coil ends uniformly in the electrically-insulative resin portions 25 around the entire circumference, making the electrically-insulative resin portions 25 assume shapes that are biased in both a circumferential and an axial direction. Thus, the heat dissipation of the coil ends including the electrically-insulative resin portions 25 is not uniform, causing the cooling of the stator winding 52 to deteriorate, and one problem has been that temperature increases in the stator winding 52 cannot be suppressed.
Because the turn portions of the strands of wire 56 constituting the coil ends are not aligned so as to be stacked in the circumferential direction, it is not possible to install the strands of wire 56 at a high density and another problem has been that high output cannot be achieved.
The turn portions of circumferentially adjacent strands of wire 56 of the stator winding groups 57A and 57C constituting the inner and outer layers are mutually offset in a radial direction, and inner circumferential surfaces and outer circumferential surfaces of the electrically-insulative resin portions 25 have irregular shapes in the circumferential direction as shown in FIG. 23. Thus, yet another problem has been that a resulting increase in wind resistance and interference occurring between the stator 7 and the inner circumferential surfaces of the electrically-insulative resin portions 25 has caused an increase in wind noise.
The present invention aims to solve the above problems and an object of the present invention is to provide an alternator which can be used in an automotive vehicle, which can achieve high output and noise reduction, and in which temperature increases in a stator winding are suppressed by constructing the stator winding from a number of winding sub-portions in each of which a long strand of wire is wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within slots at intervals of a predetermined number of slots, the strands of wire folding back outside the slots at axial end surfaces of the stator core, and by forming into a smooth surface at least one surface selected from a rotor-facing surface and a bracket-facing surface of an electrically-insulative resin portion disposed so as to cover a coil end.
In order to achieve the above object, according to one aspect of the present invention, there is provided an alternator including:
a rotor for forming north-seeking (N) and south-seeking (S) poles about a rotational circumference;
a stator including:
a stator core disposed facing the rotor; and
a stator winding installed in the stator core;
a bracket supporting the rotor and the stator; and
a cooling means for cooling the stator winding by moving together with the rotor and generating a flow of cooling air inside the bracket,
wherein
the stator core includes a laminated core formed with a number of slots extending axially at a predetermined pitch in a circumferential direction,
the stator winding includes a number of winding sub-portions in each of which a long strand of wire is wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the strand of wire folding back outside the slots at first and second axial end surfaces of the stator core to form turn portions,
the turn portions align in a circumferential direction to constitute coil ends,
an electrically-insulative resin portion is disposed so as to completely cover the coil ends, and
at least one surface of the electrically-insulative resin portion selected from a rotor-facing surface and a bracket-facing surface is formed into a smooth surface.
According to another aspect of the present invention, there is provided an alternator including:
a rotor for forming north-seeking (N) and south-seeking (S) poles about a rotational circumference;
a stator including:
a stator core disposed facing the rotor; and
a stator winding installed in the stator core;
a bracket supporting the rotor and the stator; and
a cooling means for cooling the stator winding by moving together with the rotor and generating a flow of cooling air inside the bracket,
wherein
the stator core includes a laminated core formed with a number of slots extending axially at a predetermined pitch in a circumferential direction,
the stator winding includes a number of winding sub-portions in each of which a long strand of wire is wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the strand of wire folding back outside the slots at first and second axial end surfaces of the stator core to form turn portions,
the turn portions align in a circumferential direction to constitute coil ends,
an electrically-insulative resin portion is disposed so as to cover an inner circumferential portion of the coil ends and leave an apex portion and a radially outer circumferential portion of the coil end exposed, and
a rotor-facing surface of the electrically-insulative resin portion is formed into a smooth surface.
According to still another aspect of the present invention, there is provided an alternator including:
a rotor for forming north-seeking (N) and south-seeking (S) poles about a rotational circumference;
a stator including:
a stator core disposed facing the rotor; and
a stator winding installed in the stator core;
a bracket supporting the rotor and the stator; and
a cooling means for cooling the stator winding by moving together with the rotor and generating a flow of cooling air inside the bracket,
wherein
the stator core includes a laminated core formed with a number of slots extending axially at a predetermined pitch in a circumferential direction,
the stator winding includes a number of winding sub-portions in each of which a long strand of wire is wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the strand of wire folding back outside the slots at first and second axial end surfaces of the stator core to form turn portions,
the turn portions align in a circumferential direction to constitute coil ends,
an electrically-insulative resin portion is disposed so as to cover an outer circumferential portion of the coil ends and leave an apex portion and a radially inner circumferential portion of the coil end exposed, and
a bracket-facing surface of the electrically-insulative resin portion is formed into a smooth surface.